The present invention relates to circuits for separating synchronization (sync) signals from a composite video signal, and more particularly, to such circuits in digital form.
A typical prior art sync separator uses a diode clamp circuit followed by a comparator to separate composite sync from a composite video signal and then one-shots (monostable multivibrators) to separate horizontal and vertical sync and a burst gate from the composite sync signal. While performance of such separators is generally good, it can be improved. For example, the diode clamp circuit is relatively "soft" (clamp level changes with picture content and also during the vertical sync interval) which may cause sync, and hence picture, jitter. Further, the circuits require large numbers of discrete resistors and capacitors that cannot be integrated on an integrated circuit chip.
It is therefore desirable to have a sync separator circuit that can be easily integrated and which has a fixed clamp level.